Question: If $a + b + c = 10$ and $x + y = 1$, what is $5b + 5c - 3x - 3y + 5a$ ?
$= 5a + 5b + 5c - 3x - 3y$ $= (5) \cdot (a + b + c) + (-3) \cdot (x + y)$ $= (5) \cdot (10) + (-3) \cdot (1)$ $= 50 - 3$ $= 47$